[ntp:questions] ntpd: time reset problem

David J Taylor david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Fri Sep 18 05:52:54 UTC 2009

"David Lord" <snews at lordynet.org> wrote in message 
news:7hg1jtF2s1lvqU1 at mid.individual.net...
> David J Taylor wrote:
>> You'll have to get a GPS puck and wireless PC on the roof!  Safely
> That looked a possibility earlier this year but treeline front
> and back has shot up maybe a couple of metres already and if
> same next year I'd be needing a mast.

Don't worry about trees - a modern GPS such as the GPS 18x LVC is very 
sensitive, and can work with a lot of obscuration.  Although my GPS 18 LVC 
is sitting on the roof, the GPS 18x LVC works just as well sitting in a 
room on the top floor of the house.

> I'm signed up in protest at various network over mains systems
> due to them splattering and killing QRP reception.

Me also.

> I've not mastered the demodulation though and whilst on scope
> it looks to be a clean and identifiable MSF timecode no
> different than from Conrad module, a much closer look shows
> noise spikes. I used an RC filter at output and suspect a
> Schmitt as with Maplin circuit is needed.
> David

What sort of filtering is used these days?  I used to think a 60KHz 
crystal was required, with a bandwidth of a few 10's or 100's of Hz (there 
used to be a fast-code transmission on the signal).  What's the rise-time 
required through the filter?  20ms fast enough?  A Schmitt trigger would 
be worth trying, because although there will be some hysteresis on the PC 
input port, it will be more appropriate for RS-232 levels and not tailored 
to your signal.


More information about the questions mailing list